An IVF clinic says it has been granted permission to test embryos for genetic abnormalities before they are implanted into a woman's womb, the BBC has learned.

The technique should greatly increase the chances of some women having a successful pregnancy.

For IVF this is a big step forward

Dr Mohammed Taranissi

Until now doctors have had to rely on examining the shape of embryos and the way their cells are dividing to determine which ones might contain genetic abnormalities.

However, this system is far from perfect, and up to 50% of embryos that look normal under a microscope in fact contain defects in their genetic material.

These defects can result in miscarriages, children with birth defects, or genetic conditions such as Down's syndrome.

Now doctors at the Assisted Reproduction and Gynaecology Centre in London say they have been given permission by the Human Fertilisation and Embryology Authority to remove a cell from each embryo and examine its genetic make-up far more closely.

This should enable them to predict with much greater accuracy which embryos are likely to result in a successful birth.

It means that problem embryos can be discarded, and only those with a good chance of success implanted into the woman's womb.

Selective use

Dr Mohammed Taranissi said the technique was a big step forward

Dr Mohammed Taranissi, director of the centre, said: "For IVF this is a big step forward.

"Refining the criteria by which we select embryos should dramatically reduce the chances of failure.

"It also means we can weed out problem embryos before a woman becomes pregnant."

However, Dr Taranissi said genetic screening did carry a small risk to the embryo, and would only be used on women who were thought to be at high risk.

These are likely to include women over the age of 35 with a history of recurrent miscarriages and those who have repeatedly failed to get pregnant using IVF.

As women get older their changes of producing an embryo with genetic abnormalities increases sharply. It is estimated that 70-80% of embryos produced by a woman aged 40 have genetic abnormalities.

Use of genetic screening should enable doctors to implant just one embryo at a time.

At present, doctors can implant up to three embryos in one go to maximise the chances of a successful outcome.

However, this also increases the chance that a woman will give birth to twins or triplets.

The procedure is already available in the US, where it has doubled the rate of successful pregnancy.